The present invention relates generally to a fuel pump speed controller and, more particularly, to control of a fuel pump using a dc-dc converter controlled by an integrated circuit chip.
It is well known in the art to use dc-dc converters as power supplies. Existing uses for dc-dc converters also include using such converters for driving fuel injection systems at substantial voltage levels. For example, Johnson, U.S. Pat. No. 4,576,135 discloses an electromechanical fuel injector system for use with an internal combustion engine which includes one or more electrically operated fuel injectors. The fuel injection circuitry is designed to operate from the engine storage battery; however, the injectors themselves are driven by a 60 volt dc signal, a voltage level substantially higher than the voltage of the battery to which the circuitry is connected.
Also, Speranza, U.S. Pat. No. 4,617,620, discloses an acoustic fuel injector which includes a dc-dc converter for supplying a regulated 200 volt output voltage to a frequency-controlled oscillator which drives acoustic injector valves. The oscillator circuit connects an AC pulse of closely controlled frequency and amplitude to the acoustic injector valves. The timing of the AC pulses is a function of engine speed and fuel demand and is controlled by external means not disclosed in the reference.
One existing controller for regulating the voltage applied to fuel pumps is disclosed in Furuta et al, U.S. Pat. No. 4,791,905, which controls the quantity of fuel delivered to an engine. The controller includes an electric dc fuel pump motor which is controlled by varying the electrical resistance connected in circuit between a storage battery and the motor. A fixed resistor may be selectively switched by a relay to connect the motor to the battery through the resistor or through relay contacts which short the resistor to provide no substantial electric resistance. Thus, the battery is supplied directly to the fuel pump motor during engine starting but then is switched to be supplied through a fixed resistor at a reduced voltage level thereafter for engine idle or other reduced fuel operation. In a second embodiment of the invention, the relay switch is eliminated and the fixed resistor is replaced by a variable resistor whose resistance value is continuously controlled. However, in both instances, the voltage level of power provided to the fuel pump can never be increased to a level above the battery voltage and there is a loss of efficiency in using a dropping resistor over using a dc-dc converter.
It is seen then that there is a need for a voltage regulating fuel pump speed controller which can maintain an optimal voltage level at any operating speed and battery voltage.